Two weeks after a deadly earthquake struck central-eastern Afghanistan, researchers are still trying to learn important details about the event that could help them assess the risk of future tremors in the region. A 5.9-magnitude earthquake struck at 1:24 a.m. local time on June 22 near the town of Khost, which is close to the Pakistani border. The earthquake and its aftershocks killed more than 1,000 people and destroyed thousands of homes. But the region has few seismic monitoring stations, and safety and access issues keep researchers away.
“If this earthquake had happened in Europe, we would have been there immediately – on the day of the earthquake,” says Sofia-Katerina Kufner, a geoscientist at the Karlsruhe Institute of Technology in Germany. “Speed ​​is so important. Kufner and her colleagues would use mobile seismic stations to study aftershocks and identify precise details about the location of the event. But with sparse seismic data and limited ground observations, researchers are relying more on images taken from space to study earthquakes in Afghanistan and find where the next one might strike. “We’re doing what we can with remote data, but the results will be much less accurate,” says Kufner, who plans to use satellite information.
Scientists say the devastation is unusual for a magnitude 5.9 earthquake. This was probably due to the large number of vulnerable buildings in the area, along with the shallow depth of the earthquake, estimated to be less than 10 kilometers. This resulted in intense tremors near the Earth’s surface. The timing of the tremors – at night when many people were sleeping in their homes – also contributed to the huge death toll. “A 5.9 is just a tiny event and shouldn’t kill people,” says Rebecca Bendick, a geophysicist at the University of Montana in Missoula. “If the infrastructure was better, people wouldn’t die. If the earthquake had been deeper, people would not have died. But the combination of the two was deadly.”
Uncharted territory
Because there are few seismic stations in the region, estimates of where underground earthquakes started are less accurate. The nearest seismic station is in Kabul, about 160 kilometers away, followed by one 350 kilometers away near Islamabad, Pakistan, and all others more than 500 kilometers away. Paul Earle, a seismologist who manages the US Geological Survey’s National Earthquake Information Center (NEIC) in Golden, Colorado, says the estimate of the center of the hypocenter falls within a 15-kilometer area. If an earthquake were to occur in California, where there are about 950 operating stations, it would be within 1-2 kilometers. Accurate location data helps emergency services understand the affected area more quickly, he says.
Seismic data that is available indicates that the earthquake was the result of two sides of the fault grid against each other in a horizontal “strike-slip”. However, it is unclear from this data how and in which direction the rupture propagated—information that would help identify areas that are now at increased risk of tremors. One problem is that the earthquake struck a poorly understood tectonic region, at the boundary between the Indian and Eurasian plates. The area has so many partial faults and small, unmapped fault traces that it’s difficult to identify the exact fault line, Kufner says.
It can take months to get detailed geological reports from the ground, such as evidence of changes in the Earth’s surface caused by earthquakes, and these could be washed away by heavy rains, says György Hetényi, a geophysicist at the University of Lausanne in Switzerland.
When the Taliban took power in Afghanistan in August 2021, the international community responded by suspending funding to the country, including research funding. Lack of funding, the subsequent exodus of Afghan researchers and the limited capacity of those still in the country have further hampered efforts to study the earthquake, researchers say.
NajibullahKakar, a geohazards scientist at the GFZ German Research Center for Geosciences in Potsdam, says his colleagues in Kabul are trying to restart another seismic station in the city, but they do not have access to funds to repair the damaged equipment. A temporary network of sensors designed to measure tectonic movement that Kakar and Bendick helped create in the northeast of the country in 2016 has also been destroyed and disconnected from 2021. Kakar hopes the international scientific community will find a way to help “keep the work alive.” “.
Satellite images
Without ground-based observations, Bendick thinks researchers will have a hard time learning much about earthquakes from satellite data, because it’s not useful for deciphering low-magnitude tremors. “Nobody’s really going to be able to work on that earthquake because of security and access issues,” says Bendick.But others say satellite images have already helped shed light on the details of the quake. Radar data released last week from instruments on board several satellites indicate that the rupture propagated from the epicenter in a south-southwest direction and caused several tens of centimeters of deformation on the Earth’s surface, indicating a very shallow earthquake, Hetényi says.
Source Journal Reference: Smriti Mallapaty, Deadly Afghanistan quake challenges scientists trying to study it, Nature News (2022), https://www.nature.com/articles/d41586-022-01858-x
